I just pour my own and go have fun....
While on the surface it sounds easy to punch or drill a cavity into the nose of a commercial made bullet and end up with a functional hollow point there are simply other things which keep them from preforming properly.
As mentioned above there is the chance that the core can be driven out of the jacket. Also you run the risk of expanding the outer diameter which can give you several other issues rendering the bullet no good. Then there is the core alloy being either too hard or soft to function properly for expansion in the first place.
Even pouring your own becomes a balancing and mixing act. You have to match the alloy to the pressure and velocities of your intended uses. Most use somewhere in the neighborhood of a 20-1 pure lead to tin recipe for consistent performance and expansion. While this works great for calibers such as the 45 ACP or similar low pressure lower velocity loads, bump up the horse power to something in the 1200 to 1300fps range, and you get terrible results. Not only including leading, but the noses usually simply blow right off.
When I started getting serious about pouring mine it took several attempts to get something that would reliably expand without either coming apart completely or fracturing instead of flowing. Everything has to do with the alloy. I use two different ones which I have tested in different loads from velocities of around 700fps up to around 1350fps. They are both malleable enough to flow without fracturing and they expand well within the ranges of velocities I use them for. One is softer one is a bit harder, and neither work well out of the range they were blended for.
These are a few of my higher velocity ones,
Even with jacketed bullets, say for instance simply cutting the tip back on a FMJ to expose a cavity in the nose has it's drawbacks. Usually when they impact they simply blow apart. While this might be useful on varmints, it doesn't by any stretch make them good for hunting.
All this said however if you find your project useful, then who is to say it isn't a success for your intended purpose. Just keep in mind that if your doing it for some reason of importance such as SD, or hunting, your much better off picking up the commercially available ones which have been designed expressly for the intended job.